SIRT1 activation by SRT2104 enhances mitophagy and reduces senescence in auditory cells

Age-related hearing loss is characterized by the progressive degeneration of cochlear hair cells and neurons, with mitochondrial dysfunction and impaired mitophagy implicated as molecular mechanisms. Sirtuin 1 (SIRT1), a NAD⁺-dependent deacetylase, plays a critical role in the regulation of mitochondrial quality control and mitophagy. SRT2104, a synthetic SIRT1 activator with improved bioavailability compared to resveratrol, has shown neuroprotective effects in age-related neurodegeneration. However, the role of SIRT1 in auditory cell senescence remains unclear. In this study, we investigated the effects of SRT2104 on cellular senescence and mitophagy in HEI-OC1 auditory cells and organotypic cochlear explants. Senescence was induced using low-dose H₂O₂, and SRT2104 was used as a pre-treatment. SRT2104 significantly enhanced SIRT1 activity, upregulated mitophagy-related proteins (PINK1, Parkin, BNIP3, and LC3-II), and downregulated senescence markers (p53 and p21) in cellular and explant models. β-galactosidase staining confirmed reduced senescence in SRT2104-treated groups. Pre-treatment with SRT2104 preserved mitochondrial function, as indicated by enhanced mitochondrial membrane potential, improved mitochondrial DNA integrity, and increased ATP production. SIRT1 knockdown abolished these protective effects, confirming that SRT2104 mediated its anti-senescence and pro-mitophagy activities via SIRT1. Our findings demonstrated that SRT2104 alleviates premature senescence and promotes mitophagy in auditory cells via SIRT1 activation. The pharmacological activation of SIRT1 may represent a promising therapeutic strategy to counteract age-related degeneration in the auditory system.